Pairs of oppositely rotatable ring magnets for a color television display device

ABSTRACT

A display device for colour television, comprising a correction device which is to be connected on the neck of a display tube and which comprises two pairs of diametrically magnetized rings in order to enable separate displacement of the electron beams in the tube in the horizontal and in the vertical direction.

United States Patent Vonk 1 Aug. 5, 1975 [54] PAIRS 0F OPPOSITELY ROTATABLE RING 3,341,729 9/1967 Saari 335/212 X MAGNETS FOR A COLOR TELEVISION Z1 Qmhony e 3/35/212 ,7- 3 197 arbin 335 210 x DISPLAY DEVICE 3,808,570 4/1974 Thompson et al. 335/212 Renso Vonk, Emmasingel, Eindhoven, Netherlands Inventor:

Assignee: U.S. Philips Corporation, New

York, NY.

Filed: Sept. 13, 1974 Appl. No.: 505,657

Foreign Application Priority Data Sept, 14, 1973 Netherlands 7312741 U.S. Cl 335/212; 335/210 Int. Cl. HOlf 7/00 Field of Search 335/210, 212, 213; 313/77 References Cited UNITED STATES PATENTS 10/1950 Loughren 335/212 UX Primary ExaminerG. Harris Attorney, Agent, or Firm-Frank R. Trifari; Henry I. Steckler [57] ABSTRACT A display device for colour television, comprising a correction device which is to be connected on the neck of a display tube and which comprises two pairs of diametrically magnetized rings in Order to enable separate displacement of the electron beams in the tube in the horizontal and in the vertical direction.

2 Claims, 4 Drawing Figures PAIRS OF OPPOSITELY ROTATABLE RING MAGNETS FOR A COLOR TELEVISION DISPLAY DEVICE A display device of this kind is known, for example,

from US. Pat. No. 3,725,831. The diametrically magnetized rings serve for the displacement, simultaneously and in the same direction, of the three electron beams generated by the electron guns, so that each of the beams is incident on the display screen only at areas where a phosphor is situated which luminesces in the colour associated with the relevant beam (colour purity adjustment). Because the phosphors on the display screen of a display tube comprising three electron guns which are situated in one plane (usually the horizontal plane) are usually provided in interrupted or noninterrupted stripes perpendicular to the plane of the electron guns (i.e. vertically extending), it is sufficient for the colour purity adjustment per se to displace the electron beams perpendicular to the course of the phosphor stripes, i.e. in the horizontal direction. However, it was found that a deviation of the beams in the vertical direction causes a completely different error, which becomes significant when a pattern comprising horizontal lines is displayed by the display device. In that case the horizontal lines displayed appear to be curved. This curvature can be eliminated by displacing the electron beams together in the vertical direction. It is theoretically possible to realize all combinations of horizontal and vertical displacements using two diametrically magnetized rings. However, it was found in practice that mutual influencing of the two corrections makes it very difficult to perform the two corrections satisfactorily within a reasonable period of time. Therefore, the correction is generally limited to the colour purity, and the correction of the curved horizontal line is omitted.

The invention has for its object to provide a device in which the two corrections can be simply and quickly performed, independently of each other. To this end, the device according to the invention is characterized in that the correction device comprises a second pair of permanently, diametrically magnetized rings which are rotatable about the tube axis, the fixation of the rings allowing only a rotation of the rings of each pair in opposite directions and through identical angles, the arrangement being such that the resultant magnetic field of the first ring pair is always perpendicular to the plane of the electron guns, the resultant magnetic field of the second pair always being parallel to this plane.

The first ring pair then exclusively serves for the adjustment of the colour purity, and the second pair for straightening the curved horizontal line.

The invention will be described in detail hereinafter with reference to the drawing.

FIG. 1 shows a simplified side elevation of a display device according to the invention.

FIGS. 20 and b diagrammatically illustrate the operation of the device according to the invention, and

FIG. 3 shows a section at an increased scale taken along the line III-III of the device shown in FIG. 1.

The colour television display device shown in FIG. 1 comprises a display tube, consisting of a cylindrical neck portion 1 and a flared front portion 3. The neck portion comprises three adjacent electron guns 5 (denoted by broken lines) which are situated in a horizontal plane (perpendicular to the plane of the drawing), whilst the flared portion 3 comprises a colour selection electrode (shadow-mask) 7 and a display screen 9 (also denoted by broken lines). At the area of the transition between the two tube portions a known deflection device ll is provided about the tube, a correction device 13 being provided therebehind on the tube neck 1. This correction device comprises a pair of convergence rings 15 with permanent four-pole magnetization, a pair of convergence rings 17 with permanent six-pole magnetization, and a first pair of permanently, diametrically magnetized rings 19 (two-pole magnetization) for adjusting the colour purity as described in the said US. Pat. No. 3,725,831.

According to the invention, the correction device comprises a second pair of rings 21 with two-pole magnetization which serves for the correction of vertical deviations of the electron beams combined. The resultant magnetic field of the first pair of two-pole rings 19v is always vertically directed, and that of the second pair 21 is always horizontally directed.

This is diagrammatically illustrated in FIGS. 2a and b, in which each time the position of the four poles of a pair of rings is shown with respect to the electron beams 23, 25, 27 generated by the electron guns. FIG. 2a shows that for the ring pair 19 the two north poles N (shown in one plane and on the same circle for the sake of simplicity, even though in reality they are, of course, situated on two different rings) are always situated at the same angular distances a from the vertical, the one north pole being situated to the left and the other north pole being situated to the right of the vertical. The resultant H of the two magnetic field strengths H and H generated by the rings is then also vertically directed, the angle at determining the value of H This vertical field strength causes a horizontal displacement of the electron beams 23, 25, 27 which is equally large for all beams because the field within the ring pair 19 is substantially homogeneous.

FIG. 2b shows the second ring pair 21, in which the two north poles N enclose equal and opposed angles B with the horizontal, so that the field strength H resulting from the two field strengths H and H is horizontally directed and is dependent only of B as far as its value is concerned. As a result, an equal, vertical displacement of the three electron beams 23, 25, 27 is realized.

FIG. 3 is a cross-sectional view, taken along the line III-III of FIG. 1, of a feasible structural solution for the fixation of the rings of a pair such that the said conditions are satisfied. Connected on the tube neck, using means which are known per se (not shown), is a support 29 which is common to all ring pairs 15, 17, 19, 21, and on which a holder 31 is slid. comprising a recess 33 in which a cam 35 of the support engages so that the holder cannot be rotated with respect to the support and the tube neck. The holder 31 is provided with an annular centring edge 37 with an interruption in which a pinion 41, rotatable about a shaft 39, is situated.

Present within the centring edge 37 is a first diametricallyv magnetized ring 43 having exterior teeth 45, and situated outside the centring edge is a second diametrically magnetized ring 47 having interior teeth 49. The teeth 45 and 49 engage the pinion 41, with the result that a rotation of the outer ring 47 automatically causes a rotation of, the inner ring 43 through the same angle, be'it that the latter rotation is in the opposite direction. This construction is. described in detail in the previous Netherlands Rat. Application No. 73,04,887 in the name of applioannSo as to facilitate the rotation of the outer ring 47, it is provided with four radial projections 51, one of which is provided with a notch 53 to indicate the location of thenorth pole N. Mounting is preferably effected such that the north poles N of the two rings 43, 47 are situated directly over the central electron beam 25 when thei notch 53 is situated directly over this beam. The other diametrically magnetized ring pair 21 is ,similarly constructed, be it that the two north poles N are situated in the plane of the three electron beams 23, 25, 27 when they coincide.

Besides the described construction, there are a variety of other possibilities of satisfying the requirements imposed as regards the movement of the two rings, for example, the arrangement of the rings one behind the other with an intermediate pinion, or the coupling of the movement of the rings by meansof a b'elt f lection electrode and a display screen, the neck portion having provided thereon a correction device comprising a first pair of permanently, diametrically'magnetized rings which are rotatable about the tube axis,

characterized in that the correction device (13) com-' prises a second pair (21) of permanently, diametrically magnetized rings which are rotatable about the axis of the tube (1, 3), the fixation of the ringsallowing'only a rotation of the rings of each pair (19, 21) in opposite directions and through identical angles, the arrange ment being such that the resultant magnetic'field (HQ) of the first ring pair (19) is always perpendicular to the plane of the electron guns (5), the resultant magnetic I field (H of the second pair (21) always being parallel to this plane.

2. A correction device for a display device as claimed in claim 1, characterized in that the two ring pairs (19 21 are secured to a common support (29), comprising 7 means for rigidly connecting the correction device (13) to the neck (1) of the tube. 

1. A display device for colour television, comprising a display tube having a cylindrical neck portion in which three electron guns are adjacently arranged in one plane, and a flared portion, comprising a colour selection electrode and a display screen, the neck portion having provided thereon a correction device comprising a first pair of permanently, diametrically magnetized rings which are rotatable about the tube axis, characterized in that the correction device (13) comprises a second pair (21) of permanently, diametrically magnetized rings which are rotatable about the axis of the tube (1, 3), the fixation of the rings allowing only a rotation of the rings of each pair (19, 21) in opposite directions and through identical angles, the arrangement being such that the resultant magnetic field (H19) of the first ring pair (19) is always perpendicular to the plane of the electron guns (5), the resultant magnetic field (H21) of the second pair (21) always being parallel to this plane.
 2. A correction device for a display device as claimed in claim 1, characterized in that the two ring pairs (19, 21) are secured to a common support (29), comprising means for rigidly connecting the correction device (13) to the neck (1) of the tube. 